Sink drainboard



FIG. 1 is a perspective view of a sink drainboard showing my new design;

FIG. 2 is an enlarged front elevational view of the sink drainboard shown in FIG. 1;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a side elevational view thereof, the side not shown being a mirror image of the side shown;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom view thereof. 

The ornamental design for a sink drainboard, as shown and described. 